include/linux/tracepoint.h

   1 #ifndef _LINUX_TRACEPOINT_H
   2 #define _LINUX_TRACEPOINT_H
   3
   4 /*
   5  * Kernel Tracepoint API.
   6  *
   7  * See Documentation/trace/tracepoints.txt.
   8  *
   9  * (C) Copyright 2008 Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
  10  *
  11  * Heavily inspired from the Linux Kernel Markers.
  12  *
  13  * This file is released under the GPLv2.
  14  * See the file COPYING for more details.
  15  */
  16
  17 #include <linux/errno.h>
  18 #include <linux/types.h>
  19 #include <linux/rcupdate.h>
  20 #include <linux/static_key.h>
  21
  22 struct module;
  23 struct tracepoint;
  24
  25 struct tracepoint_func {
  26         void *func;
  27         void *data;
  28 };
  29
  30 struct tracepoint {
  31         const char *name;               /* Tracepoint name */
  32         struct static_key key;
  33         void (*regfunc)(void);
  34         void (*unregfunc)(void);
  35         struct tracepoint_func __rcu *funcs;
  36 };
  37
  38 /*
  39  * Connect a probe to a tracepoint.
  40  * Internal API, should not be used directly.
  41  */
  42 extern int tracepoint_probe_register(const char *name, void *probe, void *data);
  43
  44 /*
  45  * Disconnect a probe from a tracepoint.
  46  * Internal API, should not be used directly.
  47  */
  48 extern int
  49 tracepoint_probe_unregister(const char *name, void *probe, void *data);
  50
  51 extern int tracepoint_probe_register_noupdate(const char *name, void *probe,
  52                                               void *data);
  53 extern int tracepoint_probe_unregister_noupdate(const char *name, void *probe,
  54                                                 void *data);
  55 extern void tracepoint_probe_update_all(void);
  56
  57 #ifdef CONFIG_MODULES
  58 struct tp_module {
  59         struct list_head list;
  60         unsigned int num_tracepoints;
  61         struct tracepoint * const *tracepoints_ptrs;
  62 };
  63 bool trace_module_has_bad_taint(struct module *mod);
  64 #else
  65 static inline bool trace_module_has_bad_taint(struct module *mod)
  66 {
  67         return false;
  68 }
  69 #endif /* CONFIG_MODULES */
  70
  71 struct tracepoint_iter {
  72 #ifdef CONFIG_MODULES
  73         struct tp_module *module;
  74 #endif /* CONFIG_MODULES */
  75         struct tracepoint * const *tracepoint;
  76 };
  77
  78 extern void tracepoint_iter_start(struct tracepoint_iter *iter);
  79 extern void tracepoint_iter_next(struct tracepoint_iter *iter);
  80 extern void tracepoint_iter_stop(struct tracepoint_iter *iter);
  81 extern void tracepoint_iter_reset(struct tracepoint_iter *iter);
  82
  83 /*
  84  * tracepoint_synchronize_unregister must be called between the last tracepoint
  85  * probe unregistration and the end of module exit to make sure there is no
  86  * caller executing a probe when it is freed.
  87  */
  88 static inline void tracepoint_synchronize_unregister(void)
  89 {
  90         synchronize_sched();
  91 }
  92
  93 #define PARAMS(args...) args
  94
  95 #endif /* _LINUX_TRACEPOINT_H */
  96
  97 /*
  98  * Note: we keep the TRACE_EVENT and DECLARE_TRACE outside the include
  99  *  file ifdef protection.
 100  *  This is due to the way trace events work. If a file includes two
 101  *  trace event headers under one "CREATE_TRACE_POINTS" the first include
 102  *  will override the TRACE_EVENT and break the second include.
 103  */
 104
 105 #ifndef DECLARE_TRACE
 106
 107 #define TP_PROTO(args...)       args
 108 #define TP_ARGS(args...)        args
 109 #define TP_CONDITION(args...)   args
 110
 111 #ifdef CONFIG_TRACEPOINTS
 112
 113 /*
 114  * it_func[0] is never NULL because there is at least one element in the array
 115  * when the array itself is non NULL.
 116  *
 117  * Note, the proto and args passed in includes "__data" as the first parameter.
 118  * The reason for this is to handle the "void" prototype. If a tracepoint
 119  * has a "void" prototype, then it is invalid to declare a function
 120  * as "(void *, void)". The DECLARE_TRACE_NOARGS() will pass in just
 121  * "void *data", where as the DECLARE_TRACE() will pass in "void *data, proto".
 122  */
 123 #define __DO_TRACE(tp, proto, args, cond, prercu, postrcu)              \
 124         do {                                                            \
 125                 struct tracepoint_func *it_func_ptr;                    \
 126                 void *it_func;                                          \
 127                 void *__data;                                           \
 128                                                                         \
 129                 if (!(cond))                                            \
 130                         return;                                         \
 131                 prercu;                                                 \
 132                 rcu_read_lock_sched_notrace();                          \
 133                 it_func_ptr = rcu_dereference_sched((tp)->funcs);       \
 134                 if (it_func_ptr) {                                      \
 135                         do {                                            \
 136                                 it_func = (it_func_ptr)->func;          \
 137                                 __data = (it_func_ptr)->data;           \
 138                                 ((void(*)(proto))(it_func))(args);      \
 139                         } while ((++it_func_ptr)->func);                \
 140                 }                                                       \
 141                 rcu_read_unlock_sched_notrace();                        \
 142                 postrcu;                                                \
 143         } while (0)
 144
 145 #ifndef MODULE
 146 #define __DECLARE_TRACE_RCU(name, proto, args, cond, data_proto, data_args)     \
 147         static inline void trace_##name##_rcuidle(proto)                \
 148         {                                                               \
 149                 if (static_key_false(&__tracepoint_##name.key))         \
 150                         __DO_TRACE(&__tracepoint_##name,                \
 151                                 TP_PROTO(data_proto),                   \
 152                                 TP_ARGS(data_args),                     \
 153                                 TP_CONDITION(cond),                     \
 154                                 rcu_irq_enter(),                        \
 155                                 rcu_irq_exit());                        \
 156         }
 157 #else
 158 #define __DECLARE_TRACE_RCU(name, proto, args, cond, data_proto, data_args)
 159 #endif
 160
 161 /*
 162  * Make sure the alignment of the structure in the __tracepoints section will
 163  * not add unwanted padding between the beginning of the section and the
 164  * structure. Force alignment to the same alignment as the section start.
 165  */
 166 #define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
 167         extern struct tracepoint __tracepoint_##name;                   \
 168         static inline void trace_##name(proto)                          \
 169         {                                                               \
 170                 if (static_key_false(&__tracepoint_##name.key))         \
 171                         __DO_TRACE(&__tracepoint_##name,                \
 172                                 TP_PROTO(data_proto),                   \
 173                                 TP_ARGS(data_args),                     \
 174                                 TP_CONDITION(cond),,);                  \
 175         }                                                               \
 176         __DECLARE_TRACE_RCU(name, PARAMS(proto), PARAMS(args),          \
 177                 PARAMS(cond), PARAMS(data_proto), PARAMS(data_args))    \
 178         static inline int                                               \
 179         register_trace_##name(void (*probe)(data_proto), void *data)    \
 180         {                                                               \
 181                 return tracepoint_probe_register(#name, (void *)probe,  \
 182                                                  data);                 \
 183         }                                                               \
 184         static inline int                                               \
 185         unregister_trace_##name(void (*probe)(data_proto), void *data)  \
 186         {                                                               \
 187                 return tracepoint_probe_unregister(#name, (void *)probe, \
 188                                                    data);               \
 189         }                                                               \
 190         static inline void                                              \
 191         check_trace_callback_type_##name(void (*cb)(data_proto))        \
 192         {                                                               \
 193         }
 194
 195 /*
 196  * We have no guarantee that gcc and the linker won't up-align the tracepoint
 197  * structures, so we create an array of pointers that will be used for iteration
 198  * on the tracepoints.
 199  */
 200 #define DEFINE_TRACE_FN(name, reg, unreg)                                \
 201         static const char __tpstrtab_##name[]                            \
 202         __attribute__((section("__tracepoints_strings"))) = #name;       \
 203         struct tracepoint __tracepoint_##name                            \
 204         __attribute__((section("__tracepoints"))) =                      \
 205                 { __tpstrtab_##name, STATIC_KEY_INIT_FALSE, reg, unreg, NULL };\
 206         static struct tracepoint * const __tracepoint_ptr_##name __used  \
 207         __attribute__((section("__tracepoints_ptrs"))) =                 \
 208                 &__tracepoint_##name;
 209
 210 #define DEFINE_TRACE(name)                                              \
 211         DEFINE_TRACE_FN(name, NULL, NULL);
 212
 213 #define EXPORT_TRACEPOINT_SYMBOL_GPL(name)                              \
 214         EXPORT_SYMBOL_GPL(__tracepoint_##name)
 215 #define EXPORT_TRACEPOINT_SYMBOL(name)                                  \
 216         EXPORT_SYMBOL(__tracepoint_##name)
 217
 218 #else /* !CONFIG_TRACEPOINTS */
 219 #define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
 220         static inline void trace_##name(proto)                          \
 221         { }                                                             \
 222         static inline void trace_##name##_rcuidle(proto)                \
 223         { }                                                             \
 224         static inline int                                               \
 225         register_trace_##name(void (*probe)(data_proto),                \
 226                               void *data)                               \
 227         {                                                               \
 228                 return -ENOSYS;                                         \
 229         }                                                               \
 230         static inline int                                               \
 231         unregister_trace_##name(void (*probe)(data_proto),              \
 232                                 void *data)                             \
 233         {                                                               \
 234                 return -ENOSYS;                                         \
 235         }                                                               \
 236         static inline void check_trace_callback_type_##name(void (*cb)(data_proto)) \
 237         {                                                               \
 238         }
 239
 240 #define DEFINE_TRACE_FN(name, reg, unreg)
 241 #define DEFINE_TRACE(name)
 242 #define EXPORT_TRACEPOINT_SYMBOL_GPL(name)
 243 #define EXPORT_TRACEPOINT_SYMBOL(name)
 244
 245 #endif /* CONFIG_TRACEPOINTS */
 246
 247 #ifdef CONFIG_TRACING
 248 /**
 249  * tracepoint_string - register constant persistent string to trace system
 250  * @str - a constant persistent string that will be referenced in tracepoints
 251  *
 252  * If constant strings are being used in tracepoints, it is faster and
 253  * more efficient to just save the pointer to the string and reference
 254  * that with a printf "%s" instead of saving the string in the ring buffer
 255  * and wasting space and time.
 256  *
 257  * The problem with the above approach is that userspace tools that read
 258  * the binary output of the trace buffers do not have access to the string.
 259  * Instead they just show the address of the string which is not very
 260  * useful to users.
 261  *
 262  * With tracepoint_string(), the string will be registered to the tracing
 263  * system and exported to userspace via the debugfs/tracing/printk_formats
 264  * file that maps the string address to the string text. This way userspace
 265  * tools that read the binary buffers have a way to map the pointers to
 266  * the ASCII strings they represent.
 267  *
 268  * The @str used must be a constant string and persistent as it would not
 269  * make sense to show a string that no longer exists. But it is still fine
 270  * to be used with modules, because when modules are unloaded, if they
 271  * had tracepoints, the ring buffers are cleared too. As long as the string
 272  * does not change during the life of the module, it is fine to use
 273  * tracepoint_string() within a module.
 274  */
 275 #define tracepoint_string(str)                                          \
 276         ({                                                              \
 277                 static const char *___tp_str __tracepoint_string = str; \
 278                 ___tp_str;                                              \
 279         })
 280 #define __tracepoint_string     __attribute__((section("__tracepoint_str")))
 281 #else
 282 /*
 283  * tracepoint_string() is used to save the string address for userspace
 284  * tracing tools. When tracing isn't configured, there's no need to save
 285  * anything.
 286  */
 287 # define tracepoint_string(str) str
 288 # define __tracepoint_string
 289 #endif
 290
 291 /*
 292  * The need for the DECLARE_TRACE_NOARGS() is to handle the prototype
 293  * (void). "void" is a special value in a function prototype and can
 294  * not be combined with other arguments. Since the DECLARE_TRACE()
 295  * macro adds a data element at the beginning of the prototype,
 296  * we need a way to differentiate "(void *data, proto)" from
 297  * "(void *data, void)". The second prototype is invalid.
 298  *
 299  * DECLARE_TRACE_NOARGS() passes "void" as the tracepoint prototype
 300  * and "void *__data" as the callback prototype.
 301  *
 302  * DECLARE_TRACE() passes "proto" as the tracepoint protoype and
 303  * "void *__data, proto" as the callback prototype.
 304  */
 305 #define DECLARE_TRACE_NOARGS(name)                                      \
 306                 __DECLARE_TRACE(name, void, , 1, void *__data, __data)
 307
 308 #define DECLARE_TRACE(name, proto, args)                                \
 309                 __DECLARE_TRACE(name, PARAMS(proto), PARAMS(args), 1,   \
 310                                 PARAMS(void *__data, proto),            \
 311                                 PARAMS(__data, args))
 312
 313 #define DECLARE_TRACE_CONDITION(name, proto, args, cond)                \
 314         __DECLARE_TRACE(name, PARAMS(proto), PARAMS(args), PARAMS(cond), \
 315                         PARAMS(void *__data, proto),                    \
 316                         PARAMS(__data, args))
 317
 318 #define TRACE_EVENT_FLAGS(event, flag)
 319
 320 #endif /* DECLARE_TRACE */
 321
 322 #ifndef TRACE_EVENT
 323 /*
 324  * For use with the TRACE_EVENT macro:
 325  *
 326  * We define a tracepoint, its arguments, its printk format
 327  * and its 'fast binay record' layout.
 328  *
 329  * Firstly, name your tracepoint via TRACE_EVENT(name : the
 330  * 'subsystem_event' notation is fine.
 331  *
 332  * Think about this whole construct as the
 333  * 'trace_sched_switch() function' from now on.
 334  *
 335  *
 336  *  TRACE_EVENT(sched_switch,
 337  *
 338  *      *
 339  *      * A function has a regular function arguments
 340  *      * prototype, declare it via TP_PROTO():
 341  *      *
 342  *
 343  *      TP_PROTO(struct rq *rq, struct task_struct *prev,
 344  *               struct task_struct *next),
 345  *
 346  *      *
 347  *      * Define the call signature of the 'function'.
 348  *      * (Design sidenote: we use this instead of a
 349  *      *  TP_PROTO1/TP_PROTO2/TP_PROTO3 ugliness.)
 350  *      *
 351  *
 352  *      TP_ARGS(rq, prev, next),
 353  *
 354  *      *
 355  *      * Fast binary tracing: define the trace record via
 356  *      * TP_STRUCT__entry(). You can think about it like a
 357  *      * regular C structure local variable definition.
 358  *      *
 359  *      * This is how the trace record is structured and will
 360  *      * be saved into the ring buffer. These are the fields
 361  *      * that will be exposed to user-space in
 362  *      * /sys/kernel/debug/tracing/events/<*>/format.
 363  *      *
 364  *      * The declared 'local variable' is called '__entry'
 365  *      *
 366  *      * __field(pid_t, prev_prid) is equivalent to a standard declariton:
 367  *      *
 368  *      *       pid_t   prev_pid;
 369  *      *
 370  *      * __array(char, prev_comm, TASK_COMM_LEN) is equivalent to:
 371  *      *
 372  *      *       char    prev_comm[TASK_COMM_LEN];
 373  *      *
 374  *
 375  *      TP_STRUCT__entry(
 376  *              __array(        char,   prev_comm,      TASK_COMM_LEN   )
 377  *              __field(        pid_t,  prev_pid                        )
 378  *              __field(        int,    prev_prio                       )
 379  *              __array(        char,   next_comm,      TASK_COMM_LEN   )
 380  *              __field(        pid_t,  next_pid                        )
 381  *              __field(        int,    next_prio                       )
 382  *      ),
 383  *
 384  *      *
 385  *      * Assign the entry into the trace record, by embedding
 386  *      * a full C statement block into TP_fast_assign(). You
 387  *      * can refer to the trace record as '__entry' -
 388  *      * otherwise you can put arbitrary C code in here.
 389  *      *
 390  *      * Note: this C code will execute every time a trace event
 391  *      * happens, on an active tracepoint.
 392  *      *
 393  *
 394  *      TP_fast_assign(
 395  *              memcpy(__entry->next_comm, next->comm, TASK_COMM_LEN);
 396  *              __entry->prev_pid       = prev->pid;
 397  *              __entry->prev_prio      = prev->prio;
 398  *              memcpy(__entry->prev_comm, prev->comm, TASK_COMM_LEN);
 399  *              __entry->next_pid       = next->pid;
 400  *              __entry->next_prio      = next->prio;
 401  *      ),
 402  *
 403  *      *
 404  *      * Formatted output of a trace record via TP_printk().
 405  *      * This is how the tracepoint will appear under ftrace
 406  *      * plugins that make use of this tracepoint.
 407  *      *
 408  *      * (raw-binary tracing wont actually perform this step.)
 409  *      *
 410  *
 411  *      TP_printk("task %s:%d [%d] ==> %s:%d [%d]",
 412  *              __entry->prev_comm, __entry->prev_pid, __entry->prev_prio,
 413  *              __entry->next_comm, __entry->next_pid, __entry->next_prio),
 414  *
 415  * );
 416  *
 417  * This macro construct is thus used for the regular printk format
 418  * tracing setup, it is used to construct a function pointer based
 419  * tracepoint callback (this is used by programmatic plugins and
 420  * can also by used by generic instrumentation like SystemTap), and
 421  * it is also used to expose a structured trace record in
 422  * /sys/kernel/debug/tracing/events/.
 423  *
 424  * A set of (un)registration functions can be passed to the variant
 425  * TRACE_EVENT_FN to perform any (un)registration work.
 426  */
 427
 428 #define DECLARE_EVENT_CLASS(name, proto, args, tstruct, assign, print)
 429 #define DEFINE_EVENT(template, name, proto, args)               \
 430         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 431 #define DEFINE_EVENT_PRINT(template, name, proto, args, print)  \
 432         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 433 #define DEFINE_EVENT_CONDITION(template, name, proto,           \
 434                                args, cond)                      \
 435         DECLARE_TRACE_CONDITION(name, PARAMS(proto),            \
 436                                 PARAMS(args), PARAMS(cond))
 437
 438 #define TRACE_EVENT(name, proto, args, struct, assign, print)   \
 439         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 440 #define TRACE_EVENT_FN(name, proto, args, struct,               \
 441                 assign, print, reg, unreg)                      \
 442         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 443 #define TRACE_EVENT_CONDITION(name, proto, args, cond,          \
 444                               struct, assign, print)            \
 445         DECLARE_TRACE_CONDITION(name, PARAMS(proto),            \
 446                                 PARAMS(args), PARAMS(cond))
 447
 448 #define TRACE_EVENT_FLAGS(event, flag)
 449
 450 #endif /* ifdef TRACE_EVENT (see note above) */